1.Field of the Invention
The present invention relates to a method of making a deposit on a turbomachine component made of a nickel or cobalt based superalloy.
2.Summary of the Prior Art
It is known in many situations to improve the working life of a component by applying a coating to a localized region of the component so as to improve its surface properties in this region as a function of specific stresses or contacts. Examples of surface treatment techniques of this type are described in FR-A-2397259, which proposes depositing, by fusion welding, a layer of crack-resistant alloy at the tip of a blade and then a layer of an alloy which is hard and/or resistant to oxidation corrosion. Also known from FR-A-2511908 is a diffusion-brazing assembly process for adding an element to a component made of a nickel or cobalt based superalloy, the element being in the form of a presintered blank made from a mixture of two powders, one of which, called the deposit powder, represents between 5 and 25% by weight of the mixture and comprises a nickel, chromium and boron base or a nickel, cobalt, silicon and boron base. Furthermore, US-A-4705203 describes a process for repairing surface defects in superalloy components which involves plasma flame spraying of two successive layers of different compositions and then a heat treatment during which only the first layer is melted and the surface layer is subsequently withdrawn.
The manufacturing technique described in FR-A-2511908 makes it necessary to use a homogenous mixture of powders to prepare an autobrazable sintered material which is used to form a deposit by brazing on a localized region of a superalloy component. In this case the maximum temperature at which the superalloy component is subsequently used must remain substantially lower than the brazing temperature.
Research has also been carried out to develop processes for the synthesis of either metallic, intermetallic or ceramic materials by self-propagated combustion. For example US-A-4778649 describes a process for the manufacture of a composite material in which a copper alloy layer is covered by a powder mixture layer of Ti+B+Cu, and a reaction in which TiB.sub.2 is synthesized by self-propagated combustion is triggered by compression and heating. A TiB.sub.2 surface layer and an intermediate layer of a TiB.sub.2 +Cu mixture are thus obtained on a copper substrate. Zr or Al, as well as other borides or carbides can also be used.